1. Field of the Invention
The present invention relates generally to wireless communications equipment and more particularly to a method and apparatus for controlling and maintaining a tower top low noise amplifier.
2. Description of the Related Art
When an antenna located at the top of a tower is distant from the base station communication equipment it connects to, excessive signal attenuation through tower to ground cabling can produce an increase in the signal to noise ratio of signals received by the antenna. To alleviate this problem, a tower top low noise amplifier (hereafter, xe2x80x9cTTLxe2x80x9d, not to be confused with transistor-transistor logic) is typically employed at the base of the antenna on the tower to immediately amplify receive signals and thereby prevent deterioration of signal quality. The TTL acts as a preamplifier to the main low noise amplifier (LNA) of the receiving equipment at the bottom of the tower.
Since tower top amplifiers are oftentimes difficult to access due to their location on the tower top, it is customary to utilize some sort of automatic bypassing mechanism in the event of a TTL failure. One example of such a bypassing scheme is disclosed in U.S. Pat. No. 5,418,490 which employs both primary and backup amplifiers at the tower top. The system in that patent generates a primary failure signal in the event of an abnormal current draw of the primary amplifier, whereupon the backup amplifier is automatically switched into operation. If the backup amplifier fails, a backup failure signal is generated to switch in a bypass circuit in place of the backup amplifier.
In an illustrative embodiment of the present invention, there is provided an apparatus for controlling and maintaining a tower top low noise amplifier (TTL) module coupled to an antenna, where the TTL module has a plurality of TTLs, each for amplifying signals received by the antenna on an associated cell sector. The apparatus includes a control box configured to control the TTL module and to determine whether or not an alarm condition is present, and to control bypass switches, each associated with a TTL, so as to route receive signals from the antenna to a bypass path when an alarm condition is present. An alarm board, interfaced with the control box, functions to receive data indicative of alarm conditions within the TTL module and to transmit write commands to the control box in response to commands from a base transceiver system control processor (BCP), where the write commands serve to selectively control the bypass switches within the TTL module.
An illustrative method of the present invention for controlling and maintaining a tower top low noise amplifier module coupled to an antenna includes: reading alarm information concerning alarm conditions present in the TTL module during a read mode; and, writing commands to control circuitry coupled to the TTL module in a write mode to control switching states of bypass switches therein in response to the alarm information.